It turns out that the other antibiotic I'm taking, metronidazole, has fatigue as a side effect—just what I need. Yesterday I woke up, got the kids breakfast, and flaked around for awhile. Then we went to Ikea for a couple of hours. When we got home, I slept for another three hours before dinner. At 7:30 I slept again, all night, until almost 10:00 this morning.
I think I could sleep all the time given the opportunity. Most of the time, when I think "what was I doing 12 hours ago?", the answer is "sleeping." It's insane. Fortunately I'm only taking these pills for ten days, then perhaps I'll perk up again.
It would probably be fine if I weren't so tired to start with, but compounding the fatigue I already have is more than I'd prefer to deal with. Maybe a bunch of coffee would help.